Moving coil linear actuators are well known for providing linear motion. Such actuators embody a core of soft magnetic material forming an elongated gap in which an elongated permanent magnet is disposed in contact with one of the legs of the core so as to leave a magnetic gap between the magnet and the other leg of the core. A coil of current conducting wire encircles the opposing leg of the core such that a segment of the coil side lies in the magnetic field of the magnetic gap. When a voltage is applied to the coil, the current in the coil interacts with the magnetic field and creates a force that drives the coil along the gap in a direction determined by the relative directions of the current through the coil and the north-south direction of the flux lines of the magnetic field.
For applications requiring high velocity drive along extended lengths of linear motion, it is desired to have a high magnetic field strength in the gap. This requires the use of a strong permanent magnet to create the necessary magnetic field and also a large sized, high permeability core material to support the flux created by the magnetic field without becoming saturated. Such structures become heavy and unwieldy. It is therefore desirable to provide a structure that enhances the field in the gap without adding unduly to the size and weight of the actuator or, alternatively, to reduce the size and weight of the actuator for a given gap field strength.